Multiple sources tell Eurogamer the game is already well into development, will launch in 2017, and currently holds the codename of Pokémon Stars.
Earlier generations of Pokémon games have featured a third title launched later with expanded features – Pokémon Yellow followed Game Boy originals Red and Blue to start this trend, which continued through until Pokémon Platinum followed Sapphire and Emerald on DS.

With Pokémon Stars, this idea will be revived – but for the first time we’ll see the mainline Pokémon series spanning separate Nintendo consoles within the same generation of games.

Indeed, Switch will be the first Nintendo “home” console to receive a main Pokémon adventure. It only took 20 years.